Machines for blow molding plastic bottles have a blow station at which soft, warm preforms having the general appearance of test tubes become received within larger blow cavities having the shape of the finished bottle. Pressurized air, with or without a stretch rod, is injected into the soft preforms, causing them to stretch and expand out to the limits and configuration of the blow cavities. Typically, such blow cavities are formed by opposing mold halves that are opened and closed at the beginning and end of the blow cycle, and by bottom mold surfaces on a pushup plate that closes the bottom of the cavities when the mold halves are closed. When the mold halves are opened and the pushup plate is retracted (or the blown bottles are lifted from the pushup plate in some machines), the blown bottles can be moved out of the blow station to an eject station or the like.
In a typical bottle blowing machine, the mold cavity halves are bolted to back plates that are in turn releasably secured to opposing platens of the machine that reciprocate toward and away from another at the beginning and end of the blow cycle. In order to repair one of the cavity halves, or to change out tooling for a new bottle, the heavy, unwieldy back plates with the cavity halves attached, must be unbolted from the platens and carefully extracted from the machine using overhead cranes or other assisting apparatus. Similarly, to repair or replace a pushup plate, the pushup plate must be unbolted from the actuating mechanism that extends and retracts the plate between its various positions. Depending upon the construction of the plate, certain individual mold surfaces must be unbolted from the plate before the primary mounting screws can be accessed to release and remove the pushup plate from the machine. Change out or repair of conventional tooling can thus be a very tedious, time-consuming and laborious process. It can also be costly, since no profit is generated by an idle machine.
The present invention provides quick change tooling for the blow station of a bottle making machine so as to minimize machine down time, reduce costs, and decrease delivery time for the customer who purchases new tooling. One aspect of the invention comprises having cavity halves that are quickly and easily detachable from back plates so that the back plates can remain secured to the machine platens when the cavity halves are removed during change out or repair. Preferably, instead of a series of individually bolted-on cavity halves for each back plate, a single mold block having multiple cavity halves machined therein is provided for each back plate. Each mold block has locking studs that project from the backside thereof and fit into receiving holes in the backplate. Cam locking shafts are readily accessible from the side edges of the back plates and can be quickly and easily manipulated to lock and unlock the studs of the mold block.
In another aspect of the invention, a pushup plate that forms the bottoms of the mold cavities is quickly and easily detachable from the actuating mechanism of the machine. Preferably, instead of a series of individual bottom plugs or the like bolted onto the pushup plate, the pushup plate in accordance with the present invention comprises one long plate having a multitude of plugs or other projecting mold surfaces machined thereon. The pushup plate has a pair of locking studs at opposite ends thereof that are releasably received within respective socket members affixed to the pushup mechanism of the machine and which remain with the machine when the pushup plate is changed out. Each socket member has a quick release coupling associated therewith that allows the studs of the pushup plate to be firmly and positively secured to the machine during use yet quickly and easily removed and replaced without the use of tools.